This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This will be a double-blind, placebo-controlled, within-subject, inpatient evaluation of potential interactions between intravenous cocaine and doxazosin. Interested candidates who have used cocaine by the smoked intravenous route in the past two weeks and are not seeking treatment, and are available for the 28 days of confinement as a hospital inpatient in the General Clinical Research Center (GCRC), will receive an explanation of the study purpose and requirement. If interested, the candidates will be allowed to review, inquire about and sign the informed consent. After providing signed informed consent, subjects proceed to the screening assessment phase of the study. If subjects meet all entry criteria, they will be enrolled and randomized into the study. Nontreatment-seeking cocaine dependent volunteers will be randomized to receive placebo (n=10) or doxazosin (n=10). Cardiovascular measures and subjective effects ratings will be assessed following cocaine administration.